Mechanisms of hemolysate-induced [ca2+]i elevation in cerebral
smooth muscle cells.
Zhang, He, Bryce Weir, Linda S. Marton, R. Loch Macdonald, Vytautas
Bindokas, Richard J. Miller, and James R. Brorson.
Section of Neurosurgery, Department of Surgery (H.Z., B.W., L.S.M.,
R.L.M.), Department of Neurology (J.R.B.), Department of Physiology
and Pharmacology (V.B., R.J.M.), University of Chicago, Chicago,
Illinois 60637
APStracts 2:0245H, 1995.
The effects of hemolysate on [Ca2+]i homeostasis were studied in
freshly isolated rat basilar artery smooth muscle cells using fura-2
and dual excitation wavelength microfluorimetry. Hemolysate
reversibly produced a transient [Ca2+]i peak followed by a slowly
decaying plateau which was absent in Ca2+-free solution. This effect
of hemolysate was attenuated by (1) the sarcoplasmic reticulum Ca2+
pump inhibitors thapsigargin and cyclopiazonic acid, (2) the Ca2+
-release-blocking agents ryanodine and dantrolene, (3) thecytochrome
P450 inhibitor econazole and (4) the inorganic Ca2+ channel blocker
lanthanum, but not significantly attenuated by (1) the receptor
-regulated Ca2+ channel blocker SK&F 96365 or (2) the voltage
-dependent Ca2+ channel blocker nimodipine. Fractionation of
hemolysate using membranes with specific pore sizes (0.5, 1 and 12-14
kD) indicated that a component(s) >0.5 but <1 kD could
produce a similar [Ca2+]i peak and plateau while fractions >1
and >12-14 kD produced a small and slow [Ca2+]i rise without a
significant peak. Adenosine 5'-triphosphate (ATP), which was found in
hemolysate, produced a [Ca2+]i response similar to that of
hemolysate. P2-purinoceptor antagonists significantly attenuated the
effect of ATP, hemolysate and the fractions <1 kD and <12
-14 kD. We conclude that hemolysate elevates [Ca2+]i by both releasing
Ca2+ from internal stores and triggering Ca2+ entry possibly from a
voltage-independent Ca2+ influx pathway, an effect apparently
identical to that of ATP.
Received 14 March 1995; accepted in final form 2 June 1995.
APS Manuscript Number H244-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 July 1995.